Changeover valve system having a cross drive member

ABSTRACT

A changeover valve system is provided that is adapted to be secured at one end to a riser from a pressurized piping system and at its opposite end to at least two pressure relieving devices. The changeover valve system includes a body and at least two elbows secured to the body to which are attached at least one of the pressure relieving devices. A partially spherical changeover member is provided within the body having at least one inlet port adapted to communicate with the riser and at least one and preferably two outlet ports adapted to alternately communicate with either of the pressure relieving devices. Transport means are provided for effecting rotation of the changeover member within the body to cause the changeover member to travel from one position wherein an outlet port is in communication with one of the pressure relieving devices to a second position wherein an outlet port is in communication with the other pressure relieving device. Locking means are provided for securing the changeover means in either of these two positions. A cross drive member is further provided which includes a top portion having an upper tenon for engaging the means for rotating and a bottom portion having a lower tenon for engaging the changeover member. The longitudinal orientation of the upper tenon is offset by up to about 30 degrees from the perpendicular of the lower tenon.

This is a continuation in part of U.S. patent application Ser. No.08/370,797 filed on Jan. 10, 1995 in the name of Harry E. Eminger forChangeover Valve System now U.S. Pat. No. 5,549,138.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a changeover valve systemhaving a cross drive member and, more specifically, to a suitable andefficient three-way, changeover valve system that is adapted to bemounted on a pressurized piping system. The changeover valve system ofthe present invention is mounted on a single pipe riser in thepressurized piping system and includes at least two independent pressurerelieving devices such as, for example, pressure relief valves. Thechangeover valve system is adapted to permit the transfer of the activepressure relieving function from one pressure relieving device to theother pressure relieving device during operation of the pressurizedpiping system using the cross drive member without jeopardizing thepressure relieving capability of the pressurized piping system.

2. Description of the Prior Art

The prior art fails to specifically address either the problems or thesolutions arrived upon by applicant. For example, Fetterolf Corporationhas marketed a horizontal stem double-seated globe valve called aRam-Seal Valve that provides a high pressure drop or resistance to flow.Due to its configuration, it is often necessary to use oversized valvesto provide the required flow capacity. In addition, valves of thisconfiguration have a large envelope size which limits their application.

In cases where a second changeover valve is connected to the outlets ofthe pressure relieving devices mounted on the first changeover valve ina tandem arrangement, there must be a simultaneous mechanical operationof the changeover valves in order to maintain the over pressureprotection for the system.

With the Fetterolf and similar designs, it is difficult to coordinatethe seating positions in a tandem arrangement and automation isdifficult or impossible. Further, it is often difficult to seal longrising or multiple rotation stems.

One similar type valve is marketed by FEMA designated as Valvola diScambio.

Anderson, Greenwood & Co. has marketed a changeover valve that utilizesa flat closure disc with a vertical "Y" type design. In such anarrangement, the valve stem must be driven down sufficiently to permitthe disc to be rotated 180 degrees to the opposite seat and thenretracted in an upward direction to close the disc to the seat. Suchoperation is complex and requires torque measuring devices to meet themanufacturer's operating specifications. The number of stem rotationsrequired to raise and lower the disc and the 180 degree rotationrequired to change flow positions precludes the application of anintegral manual operating handle.

Moreover, the multiple operations that are required (i.e., lowering,rotating and raising) effectively precludes remote actuation of a singlevalve and is even more complex in tandem applications.

Further, in such a design, the application of reverse pressurization totest the set pressure of the isolated pressure relief device tends toforce the disc away from the seat and add loads to the operatingmechanism. Therefore, it may not be possible to pressurize and test suchpressure relieving devices in place when mounted.

Another example of a selector valve is described in U.S. Pat. No.4,821,772 which issued on Apr. 18, 1989 to William L. Anderson, Jr.,entitled Dual Active Selector Valve. The Anderson '772 patent describesthe Anderson Greenwood valve previously discussed. In particular, itshows additional flow passages if more than one active pressurerelieving device is desired.

Other examples of multiple outlet or shuttle valves include thosedescribed in U.S. Pat. No. 5,329,968 which issued on Jul. 19, 1994 toWalter W. Powell entitled Shuttle Valve and U.S. Pat. No. 4,403,626which issued on Sep. 13, 1983 to Herman L. Paul, Jr. entitled ValveAssembly.

Examples of ball valves include those described in U.S. Pat. No.5,251,663 which issued on Oct. 12, 1993 to Rollin C. Christianson et al.entitled High-Temperature, High-Pressure Oxygen Metering Valve; U.S.Pat. No. 4,915,133 which issued on Apr. 10, 1990 to C. L. Scott Harrisonentitled Valve Device for Piping Systems; U.S. Pat. No. 4,881,718 whichissued on Nov. 21, 1989 to Raymond P. Champagne entitled Ball ControlValve; U.S. Pat. No. 4,441,524 which issued to Hisayoshi Mese on Apr.10, 1984 entitled Ball Valve; U.S. Pat. No. 4,203,572 which issued toRonald D. Coffman on May 20, 1980 entitled Locking Ball Valve; U.S. Pat.No. 3,345,032 which issued on Oct. 3, 1967 to W. W. Rawstron entitledThree-Way Ball Valve; U.S. Pat. No. 3,537,473 which issued on Nov. 3,1970 to David B. DeZurik, Jr. entitled Anti Slam Valve PositioningMeans; U.S. Pat. No. 3,184,213 which issued on May 18, 1965 for CliffordE. Anderson entitled Seat For Top Entry Ball Valve; and U.S. Pat. No.3,100,499 which issued on Aug. 13, 1963 to Harold E. Bass entitledValve.

As will be appreciated, none of the valve systems heretofore describedteach or suggest the use of a three-way, changeover valve that offersthe unique advantages presented by the changeover valve system of thepresent invention.

SUMMARY OF THE INVENTION

Against the foregoing background, it is a primary object of the presentinvention to provide a pressure relieving changeover valve system thatis adapted to be used in combination with a pressurized piping system.

It is another object of the present invention to provide such achangeover valve system of a partial ball-type configuration.

It is yet another object of the present invention to provide such achangeover valve system that is adapted to accommodate at least twopressure relieving devices.

It is still another object of the present invention to provide such achangeover valve system that is adapted to direct a single source offluid to either of the pressure relieving devices.

It is another object of the present invention to provide such achangeover valve system with minimal flow resistance.

It is yet still another object of the present invention to provide sucha changeover valve system that is adapted to permit one of the pressurerelieving devices to be serviced without affecting the integrity of theover pressure relieving capability of the pressurized piping system.

It is yet another object of the present invention to provide such achangeover valve system that is operated by minimized rotational motiononly.

It is but still another object of the present invention to provide sucha changeover valve system that may include an integral and visiblecontrol handle for manually changing from one pressure relieving deviceto the other pressure relieving device during operation.

It is still another object of the present invention to provide such achangeover valve system that may be adapted to the use of gearedactuators or powered actuators.

It is but another object of the present invention to provide such achangeover valve system that permits in situ adjustment of the setpressure of the installed isolated pressure relieving device.

It is but yet another object of the present invention to provide such achangeover valve system that includes means for balancing the pressureto minimize operating forces.

It is but still yet another object of the present invention to providesuch a changeover valve system in which the inlet port is alwaysconnected to one of the outlet ports to achieve a fail-safeconfiguration.

It is yet still another object of the present invention to provide sucha changeover valve system in which one may change from one pressurerelieving device to another pressure relieving device withoutcompromising the over pressure protection of the piping system duringthe changeover process.

It is but another object of the present invention to provide such achangeover valve system in which a cross drive member is used to effectmovement of the changeover member.

To the accomplishments of the foregoing objects and advantages, thepresent invention, in brief summary, comprises a changeover valvesystem, having a cross drive member, that is adapted to be secured atone end to a riser from a pressurized piping system and at its oppositeend to at least two pressure relieving devices. The changeover valvesystem includes a body and at least two elbows secured to the body towhich are attached to at least one of the pressure relieving devices. Apartially spherical changeover member is provided within the body havingat least one inlet port adapted to communicate with the riser and atleast one, but preferably two, outlet ports adapted to alternatelycommunicate with each of the pressure relieving devices. Transport meansincluding a cross drive member are further provided for effectingrotation of the changeover member within the body to permit thechangeover member to travel from a first position in which the outletport is in communication with one of said pressure relieving devices toa second position in which the outlet port is in communication with theother pressure relieving device. In intermediate positions between thefirst and second positions, the at least one outlet port always remainsin communication with at least one of said pressure relieving devices.Locking means are provided for securing the changeover means in eitherof these two positions but not in any intermediate position.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and still other objects and advantages of the presentinvention will be more apparent from the detailed explanation of thepreferred embodiments of the invention in connection with theaccompanying drawings, wherein:

FIG. 1 is a perspective view of the changeover valve system of thepresent invention;

FIG. 2 is a top view of the changeover valve system of the presentinvention;

FIG. 3 is a sectional view taken along line 3--3 of FIG. 2;

FIG. 4 is a sectional view taken along line 4--4 of FIG. 2;

FIG. 5 is an enlarged top view of the partially spherical changeovermember of the changeover valve system of the present invention;

FIG. 6 is an enlarged perspective view of the cross drive pin used forconnecting the valve stem to the changeover member of the changeovervalve system of the present invention;

FIG. 7 is a top view of the stop plate of the changeover valve system ofthe present invention;

FIG. 8 is a side view of the stop plate of FIG. 7;

FIG. 9 is a side sectional view of the handle assembly taken along line9--9 of FIG. 2;

FIG. 10 is a side sectional view of handle assembly of the changeovervalve system of the present invention;

FIG. 11 is a sectional view of the handle assembly taken along line11--11 of FIG. 10;

FIG. 12A is a top view of the locking handle of the balance valveprovided on the changeover valve system of the present invention;

FIG. 12B is a side sectional view of the locking handle of the balancevalve taken along line 12B--12B of FIG. 12A;

FIG. 13 is a schematic illustration of the balance piping arrangementemployed in the changeover valve system of the present invention;

FIG. 14 is an exploded perspective view illustrating the interaction ofthe cross drive member and the partially spherical changeover member ofthe changeover valve system of the present invention;

FIG. 15 is a top view illustrating the partially spherical changeovermember with the cross drive member in a first position; and

FIG. 16 is a top view of the partially spherical changeover memberrotated to a second position.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and, in particular, to FIG. 1 thereof, thereis provided a ball-type changeover valve system referred to generally byreference numeral 10. The changeover valve 10 of the present inventionis secured to a single riser 1 leading from a pressurized piping orconduit system (not shown).

The changeover valve 10 includes a body 12, a bonnet 13 affixed to thebody 12 by bolts 4 and sealed by seal 47, a partially sphericalchangeover member 20, and at least two outwardly extending elbows 14.Each of these outwardly extending elbows 14 have a flange 16 at theiroutward ends to facilitate attachment of the changeover valve 10 to atleast two pressure relieving devices (not shown). The subject changeovervalve 10 may be used in conjunction with such pressure relieving devicesas pressure relief valves or non-reclosing pressure relieving devicessuch as, for example, rupture discs.

It should be appreciated that the elbows 14 and flanges 16 may be weldedor otherwise secured or attached to the changeover valve 10. Flowpassageways 15 and 17 are provided within the elbows 14 and flanges 16to permit communication between the riser 1 of the pressurized pipingsystem and the pressure relieving devices.

During actual operation of the changeover valve 10, two pressurerelieving devices are mounted on the valve flanges 16. The changeovervalve 10 is similarly mounted to the riser 1 by means of a gasketsurface and appropriate threaded bolt holes 3 (See FIG. 3) provided inthe bonnet 13, or by welding a prepared surface of the bonnet 13directly to the riser 1 or by other suitable mounting means.

As shown in greater detail in FIGS. 3-5, changeover member 20 isprovided having a spherical outer surface 21. At least two outlet ports22, 24 are provided in the changeover member 20 which communicate with alower inflow port 25 at the bottom of the changeover member 20. Thespecific sizes and locations of the outlet ports 22, 24 are selected todictate the amount of rotation that the changeover member 20 must travelfrom a first position in which one of the outlet ports 22,24 is alignedwith one of the flow passageways 15,17 to a second position in which theother of the outlet ports is aligned with the other of the flowpassageways. A recess 26 is also provided in the changeover member 20.

In actual operation of the changeover valve 10, at least one outlet port22,24 is always in at least partial communication with at least one ofthe flow passageways 15,17 leading to a pressure relieving device. Thus,as the changeover valve 10 rotates from the first position to the secondposition, the flow from the piping system is diverted from one pressurerelieving device to the other. At no time, however, are both outletports 22, 24 totally closed. Similarly, the inflow port 25 alwaysremains in communication with the riser 1. Accordingly, at no timeduring the changeover operation is the pressure relieving capability ofthe pressurized piping system compromised and a fail-safe condition isachieved.

In a preferred embodiment, the amount of rotation required to changeoverfrom one pressure relieving device to the other pressure relievingdevice is approximately 76 degrees although this may vary depending uponthe application, the dimensions of the diameter of the flow passageways15,17, and the diameter of the seat face contact on the changeovermember 20.

As shown in greater detail in FIG. 3, the changeover member 20 iscontrollably loaded into a seat assembly 30, having a seat 32 which issealed to seat carrier 31 by O-ring 33 with interposing spring 37 andO-ring carrier 35 is further sealed to seat carrier 31 by o-ring 34 andto body 12 by o-ring 36, by the load ring 40 that is threaded into thebody of the valve through thrust washer 45. In a final assembledposition, the load ring 40 is locked to the body 12 of the changeovervalve 10 by set screw 46.

In a preferred embodiment, the seat assemblies 30 are fabricated astwo-piece assemblies to provide a flexible, bi-lateral joint motionwhich insures that the separable seat 32 makes intimate contact andseals with the spherical surface of the changeover member 20. It will beappreciated that the seat assemblies 30 may be of multiple parts withnon-metallic inserted seats 32, single piece seat assemblies withinserted non-metallic seat faces, or single piece metallic seats 32virtually of any material including such non-metallic materials ascarbon, graphite and ceramic as well as plastic materials. It will beappreciated that a one piece seat assembly may be used although such anassembly may not seal as well as the two-piece assembly. Final selectionof materials and configurations will, of course, depend upon thespecific application for the changeover valve 10.

When the changeover valve 10 is pressurized from either outlet flange 16as would occur, for example, when adjusting the set pressure of a reliefvalve in place, the seat assemblies 30 are independent from the body 12to enable the differential pressure to urge the seat 32 tightly againstthe spherical surface 21 of the changeover member 20. The springs 37also aid in applying pressure against the seat 32 to effect a tighterseal. The seat assemblies 30 are specifically designed to have amultiplying piston effect on the seat load under such conditions. Inother words, the piston area of the seat assemblies 30 is greater thanthe seat 32 contact area on the changeover member 20 and, therefore, thesealing pressure between the seat 32 and the surface of the changeovermember 20 is always higher than the value of the pressure to be sealed.

The rotation or movement of the changeover member 20 from the firstposition to the second position is performed manually by manipulation ofa handle assembly 70 provided at the top of the changeover valve 10. Thehandle assembly 70 is interconnected to the changeover member 20 by avalve stem 50 having a cross drive pin 54 provided at its end oppositethe handle assembly which is adapted to engage a rectangular, matchingrecess 26 at the top of the changeover member 20 (see FIG. 4). Thispermits the changeover member 20 and the valve stem 50 to rotate ontheir respective centers. The valve stem 50 has an integral shoulderwhich bears on the stem bearing 52 and provides lateral support andprevents the valve stem 50 from blowing out of the assembly. The valvestem 50 is further sealed to the body 12 of the changeover valve 10 bypacking or seals 60.

The handle assembly 70 attached to the valve stem 50 serves tofacilitate the movement of the changeover member 20 between positions.By moving the handle assembly 70 from one position to another (as shownin FIG. 2), the changeover member 20 is able to function and rotatebetween the first and second positions, e.g., from a first positionwhere one outlet port 22,24 communicates with one flow passageway 15,17leading to one pressure relieving device to a second position where theother outlet port communicates with the other flow passageway leading tothe other pressure relieving device. At no time during such changeover,however, are both outlet ports 22,24 completely closed which wouldcompromise the piping systems over pressure relieving capability. It isonly when the changeover is complete and the changeover member 20assumes its second position that the first outlet port communicatingwith one pressure relieving device is completely closed and the secondoutlet port communicating with the second pressure relieving device iscompletely opened. In intermediate positions between the first andsecond position, each outlet port would be partially open.

As shown in greater detail in FIGS. 9-11, handle assembly 70 includes atube 72 that is slidably engaged over a handle 73 so as to provide alonger lever arm when the tube 72 is extended from the handle 73 forfacilitating valve actuation. When collapsed, the handle assembly 70serves to enclose and therefore protect the handle nut 74 (See FIG. 4)to prevent access to and inadvertent removal of the handle assembly 70.

When the handle assembly 70 is collapsed, a locking lug 75 having alocking hole 87 integral to the sliding handle 72 comes into positionover and mates with a complementary matching hole 88 in a stop plate 78on which the handle assembly 70 operates and a complementary hole in thebalance valve locking handle 86 and permits a locking device 80 such asa lock to be inserted through the complementary holes for securing thechangeover member 20 into a fixed position. It will, of course, beappreciated that the locking device 80 may only be inserted when thevalve handle assembly 70 is in a proper closed position thereby insuringthat locking will only occur in either the first or second positionwhere the changeover valve 10 is in full communication with either ofthe pressure relieving devices and not in any intermediate positionwhere both outlet ports are partially open.

The stop pins 77 (see FIG. 2), which are adjustably secured to the stopplate 78, provide adjustable stops to limit the travel of the handleassembly 70. Further, when the locking handle 86 is collapsed, itengages the front stop pins 77 and locks the handle 86 in place therebypreventing inadvertent rotation.

The outer end of the tube 72 of the handle assembly 70 is painted(preferably bright red) and provides a highly visible indication ofwhich pressure relieving device is active since the red outer tube 72 isdesigned to sit immediately under the active pressure relieving device.

It will be appreciated that in another embodiment of the presentinvention, the outer reduced section of the handle 73 may be painted(preferably green) and only becomes visible when the sliding tube 72 isin the fully collapsed position for locking with the locking device 80and is not otherwise visible.

It may further be appreciated that a locking device 80 may,alternatively, be used through a pair of the complementary holes in thevalve system to lock the changeover member 20 of the changeover valve 10in a proper operating position.

Since the changeover member 20 is pre-loaded into the seat assembly 30and is further urged therein by pressure when the changeover valve 10 isin either relief position, it should be appreciated that the operatingtorque necessary to move the changeover member 20 from one position tothe other can be high. Accordingly, a balance valve 85 with valve handle86 (see FIGS. 12A and 12B) is provided to balance the pressure above andbelow the changeover member 20 prior to operation of the changeovervalve 10. In a preferred embodiment, the balance valve 85 is a simpleball valve that is operated by a balance valve handle 86 which includesan aperture 89 through which the locking device 80 may pass to engageand lock this handle 86. It should be noted that the configuration ofthe balance valve handle 86 is such that the valve system 10 of thepresent invention cannot be locked in either the first or secondposition by locking device 80 unless the balance valve handle 86 is inthe proper position to close the communication of pressure betweenpassageways 15. Aperture 89 on the balance valve handle 86 must be fullyaligned with aperture 87 in the handle 70 and aperture 88 in lockingplate 78 to permit the insertion of the locking element 80 through saidapertures. This is only accomplished when the balance valve 85 is insuch proper position to close communication of pressure betweenpassageways 15. This is extremely important because if the balance valve85 is not in such position to close communication of pressure betweenpassageways 15, a potentially hazardous condition could occur. Thisfeatures serves as a fail-safe feature of the present invention.

As shown in the schematic of the balance valve system in FIG. 13, thebalance valve 85 is connected by a pipe or tube to flow passageways 15of the valve system 10 above the seat assemblies 30. The normaldirection of pressure is from the single port at the bottom of thechangeover valve 10.

As a result of the utilization of this balance valve 85, it is possibleto greatly reduce the torque required to operate the changeover valvesystem 10 by a simple hand lever or smaller and more economical gearedor powered actuators when the balance valve 85 may, for example, be asolenoid operated valve. Without the use of such a balance valve system,it might not be possible to operate the valve system 10 by hand, in mostapplications.

Vent valves 110 are further provided communicating with the flowpassageways 15. These vent valves 110 permit the pressure in theisolated flow passageway 15 to be vented prior to removal of theisolated relief valve. In addition, they serve as tell tales to walk upto and open to make sure that the changeover member 20 has seatedproperly beneath the isolated pressure relieving device. They also serveas a pressure relieving device pressurizing point for in situ testing.

The aforementioned configuration for this changeover valve 10 permitsuse in conjunction with at least two pressure relieving devices so as toprovide for continuous process maintenance even though a pressurerelieving device may leak and need to be replaced. This is done by: (1)unlocking the slidable tube 72 from the handle assembly 70, the balancevalve locking handle 86 and the stop plate 78 and extending the slidabletube 72 from the assembly 70; (2) balancing the pressure in the valvesystem by operating the balance valve handle 86; (3) manipulating thehandle assembly 70 from one position against one stop pin 77 to theopposite position against the opposite stop pin 77 thereby causing thechangeover member 20 to rotate counterclockwise (or clockwise); (4)collapsing the handle assembly 70; (5) closing the balance valve 85; (6)re-inserting the locking device in the new position; and (7) venting thecavity above the isolated seat to the atmosphere by the appropriate ventvalve 110.

The isolated pressure relieving device may then be removed and repairedor replaced in readiness for the next situation in which the activerelieving device may require maintenance. This process may be repeatedover and over without having to effect over pressure protection orstopping an operating process system.

FIGS. 14-16 illustrate in greater detail an alternative embodiment ofthe present invention which employs a novel cross drive member 200having a top portion having an upper tenon 202 and a bottom portionhaving a lower tenon 204 in combination with a partially sphericalchangeover member 220. The lower tenon 204 of the cross drive member 200is adapted to engage recess 226 in changeover member 220. An inherentproblem relates to the transmission of rotary motion to the sphericalchangeover member 220 between the two positions of operation withoutrestricting radial or axial motion between the valve stem and theclosure member. This must be accomplished while providing as little lostmotion or backlash as possible in the rotational plane to insureaccurate seating positions at the limits of the rotational travel.

It has been found that by offsetting the upper tenon 202 of the topportion of the cross drive member 200 relative to the lower tenon 204 ofthe bottom portion as shown in FIGS. 14-16, transmission of rotarymotion to the changeover member 220 is accomplished with minimal lostmotion, minimum impact on the seating and minimal leakage. In apreferred embodiment, the upper tenon 202 is offset up to 30 degreesfrom the perpendicular of the lower tenon 204. In a particularlypreferred embodiment, the upper tenon 202 is offset approximatelybetween 10 and 20 degrees from the perpendicular of the lower tenon 204and preferably 14 degrees from its perpendicular.

As can be seen in FIGS. 15-16, the offset of the upper tenon 202 doesnot alter the relationship of the cross drive in its initial seatingposition as shown in FIG. 15 where port 224 is open When the changeovermember 220 is rotated approximately 76 degrees clockwise to a secondposition as shown in FIG. 16 in which port 222 is open, the top portionof the cross drive sliding in the stem slot provides direct radialmotion of the closure member to the seat and, therefore, the seat loadbias previously described is removed. This has been found to minimizevalve leakage problems

Having thus described the invention with particular reference to thepreferred forms thereof, it will be obvious that various changes andmodifications can be made therein without departing from the spirit andscope of the present invention as defined by the appended claims.

Wherefore, I claim:
 1. A changeover valve system adapted to be securedat one end to a riser from a pressurized piping system and at itsopposite end to at least two pressure relieving devices, said systemincluding:a body; at least two outlets secured to said body, each ofsaid outlets being attached to a pressure relieving device; a partiallyspherical changeover member provided within said body, said changeovermember having at least one inlet port adapted to communicate with saidriser and at least one outlet port adapted to alternately communicatewith each of said pressure relieving devices; and means for rotatingsaid changeover member within said body so as to cause said changeovermember to move from a first position in which said at least one outletport is in communication with one of said pressure relieving devices toa second position in which said at least one outlet port is incommunication with said other pressure relieving device, wherein saidmean for rotating includes a cross drive member for engaging saidchangeover member.
 2. The changeover valve system of claim 1, whereinsaid cross drive member includes a top portion having an upper tenon forengaging said means for rotating and a bottom portion having a lowertenon for engaging said changeover member.
 3. The changeover valvesystem of claim 2, wherein the longitudinal orientation of said uppertenon is offset by up to about 30 degrees from the perpendicular of saidlower tenon.
 4. The changeover valve system of claim 3, wherein thelongitudinal orientation of said upper tenon is offset by between about10 degrees and about 20 degrees from the perpendicular of said lowertenon.
 5. The changeover valve system of claim 1, further including abalance valve for balancing the pressure above and below the changeovermember prior to operation of the changeover valve.
 6. The changeovervalve system of claim 5, wherein said balance valve includes a balancevalve locking lever handle.
 7. A changeover valve system adapted to besecured at one end to a riser from a pressurized piping system and atits opposite end to at least two pressure relieving devices, said systemincluding:a body; at least two outlets secured to said body, each ofsaid outlets being attached to a pressure relieving device; a partiallyspherical changeover member provided within said body, said changeovermember having at least one inlet port adapted to communicate with saidriser and at least one outlet port adapted to alternately communicatewith each of said pressure relieving devices, said changeover memberbeing adapted to rotate from a first position in which one of saidoutlet ports is in communication with a pressure relieving device to asecond position wherein said other outlet port is in communication withanother pressure relieving device; and means for effecting rotation ofsaid changeover member within said body so as to cause said changeovermember to move from said first position to said second position, saidmeans for effecting rotation including a cross drive member with a topportion having an upper tenon for engaging said means for rotating and abottom portion having a lower tenon for engaging said changeover member,wherein the longitudinal orientation of said upper tenon is offset by upto about 30 degrees from the perpendicular of said lower tenon.
 8. Thechangeover valve system of claim 7, wherein the longitudinal orientationof said upper tenon is offset by between about 10 degrees and about 20degrees from the perpendicular of said lower tenon.
 9. The changeovervalve system of claim 7, further including a balance valve for balancingthe pressure above and below the changeover member prior to operation ofthe changeover valve.
 10. The changeover valve system of claim 9,wherein said balance valve includes a balance valve locking leverhandle.
 11. A changeover valve system adapted to be secured at one endto a riser from a pressurized piping system and at its opposite end toat least two pressure relieving devices, said system including:a body;at least two outlets secured to said body, each of said outlets beingattached to a pressure relieving device; a partially sphericalchangeover member provided within said body, said changeover memberhaving at least one inlet port adapted to communicate with said riserand at least one outlet port adapted to alternately communicate witheach of said pressure relieving devices, said changeover member beingadapted to rotate from a first position in which one of said outletports is in communication with a pressure relieving device to a secondposition wherein said other outlet port is in communication with anotherpressure relieving device; means for effecting rotation of saidchangeover member within said body so as to cause said changeover memberto move from said first position to said second position, said means foreffecting rotation including a cross drive member with a top portionhaving an upper tenon for engaging said means for rotating and a bottomportion having a lower tenon for engaging said changeover member,wherein the longitudinal orientation of said upper tenon is offset by upto about 30 degrees from the perpendicular of said lower tenon; and abalance valve for balancing the pressure above and below the changeovermember prior to operation of the changeover valve.
 12. The changeovervalve system of claim 11, wherein the longitudinal orientation of saidupper tenon is offset by between about 10 degrees and about 20 degreesfrom the perpendicular of said lower tenon.
 13. The changeover valvesystem of claim 12, wherein said balance valve includes a balance valvelocking lever handle.
 14. A cross drive member for use in conjunctionwith a changeover valve system of the type having a body; at least twooutlets secured to said body, each of said outlets being attached to apressure relieving device; a partially spherical changeover memberprovided within said body; and means for effecting rotation of saidchangeover member within said body, wherein said cross drive memberincludes a top portion having an upper tenon for engaging said means forrotating and a bottom portion having a lower tenon for engaging saidchangeover member, wherein the longitudinal orientation of said uppertenon is offset by up to about 30 degrees from the perpendicular of saidlower tenon.
 15. The changeover valve system of claim 14, wherein thelongitudinal orientation of said upper tenon is offset by between about10 degrees and about 20 degrees from the perpendicular of said lowertenon.
 16. The changeover valve system of claim 14, further including abalance valve for balancing the pressure above and below the changeovermember prior to operation of the changeover valve.
 17. The changeovervalve system of claim 16, wherein said balance valve includes a balancevalve locking lever handle.